1. Field of the Invention
The present invention relates to a display device for allowing a viewer to see a real image of an object of view formed in the air by using an imaging optical system of real specular image.
2. Description of the Related Art
A display device is suggested (see WO2007/116639), in which a viewer is allowed to see a real image of an object of view, i.e., real specular image formed in the air by using an imaging optical system of real specular image.
This display device includes an object of view arranged in a space opposite to a viewer, and an imaging optical system of real specular image for forming a real image of the object of view in a space in which the viewer exists. A real image of the object is formed at a position symmetrical to the object with respect to a plane of symmetry (element surface) of the imaging optical system of real specular image.
In one example, a floating image is presented in a space in front of an image display surface such as that of an electronic display, or in a space in front of a display device of some kind of equipment such as an instrument panel of an automobile (namely, in a space in which a driver (viewer) exists). This will be regarded as suggesting a new way of image display. As a specific example, while watching a situation outside an automobile through a windshield while driving, a driver sometimes looks at an instrument panel to check on a speed, the number of revolutions of an engine, time and others. In the case, for example, of overspeed, it is assumed that a floating indication for calling attention is given in a space in front of the instrument panel in which nothing is originally expected to exist. This attracts attention of the driver more than an indication given on the instrument panel showing the overspeed, thereby contributing to prevention of traffic accidents.
The present inventors have suggested a display device (as Japanese Patent Application No. 2008-70415). According to this display device, a display part and an object of view are spatially separated, and an indication on the display part and a real image of the object formed by an imaging optical system of real specular image are simultaneously displayed in the sightline of a viewer. This means that the viewer is allowed to see a real image of the object formed in front of the display part, while seeing the display part arranged on a back wall behind the real image. In this display device, the viewer normally sees only the display part, and a real image of the object is formed in a space in front of the display part only on the occurrence of a certain event, for example. In this case, an image appears in the space in which nothing is originally expected to exist. This provides a way of image view that more attracts attention of the viewer.
However, even if the method disclosed in WO2007/116639 is applied to this display device, an imaging optical system of real specular image is still required behind a real image in order to see a real image. Accordingly, the viewing location of the viewer is limited to a position tilted 45 degrees from the element surface of the imaging optical system of real specular image. This means that an indication on the display part on the back wall and a real image cannot be superimposed when seen by the viewer.
Furthermore, the imaging optical system of real specular image can only form real images, meaning that an impressive image such as the one that is partially made stereoscopic cannot be formed.
In the method of WO2007/116639, a resultant floating image is fixed in position and in size as an object of view is fixed. Accordingly, except for being a floating image, the resultant image is not impressive.